Beneficiation of potash ores



May 16, 1961 A. ADAMS ETAL BENEFICIATION oF PoTAsH oREs Filed Aug. 14,195s Patented May 16, 1961 BENEFHCIATION F PO'IASH DRES Albert Adams andWilliam B. Dancy, Carlsbad, N. Mex.,

assignors to International Minerals d; Chemical Corporation, acorporation of New York Filed Aug. 14, 1958, Ser. No. 755,111

12 Claims. (Cl. 209-12) The present invention generally relates to thebenelication of potash ores. More particularly, it relates to animproved process for the separation of sylvite from ores of thesylvinite type, for example such ores as are mined in the Carlsbaddistrict of New Mexico.

As is well known, potash is of great economic importance. Extensivedeposits of potash salts are found on every continent. However, inpractically no instance is the potash salt found in a substantially pureform. On the North American continent, one frequently encountered potashsalt is sylvite (KCl). The KCl is not often found in any appreciablequantities as pure sylvite ore but is most often found as sylvinite ore,which is a mixture of sylvinite and halitc (NaCl). A typical analysis ofa sylvinite ore is as follows:

Other constituents or impurities consisting of silicates,

sulfates, etc. 4

This invention is of particular value in connection with processes ofthe general type disclosed in the Tartaron, Cole and Duke Patent No.2,288,497. Said patent describes a process which comprises suspendingcomminuted sylvinite ore in a circulating saturated brine formed bydissolving the soluble constituents of the ore in water and thenfloating the particles of sylvite by means of a suitable collector agentWhile permitting the particles of halite to settle. The type of processto which this invention relates is thus distinguished from that type ofprocess disclosed in the Weinig Patent No. 2,222,331, issued November19, 1940, in which the halite is floated and the sylvite is settled.

In processes of this general character, it has been the general practiceto grind the ore to a rather line mesh, for example, to a degree ofneness Where at least 90% of the ore would pass through a sieve of about40 mesh. Flotation of the valuable sylvite constituents of an ore ofsuch degree of lineness is not too dillicult a problem, and varioustypes of collector agents for effecting such flotation can be used. Itis, however, very costly to thoroughly size an ore so that substantiallyall of the ore particles to the flotation process fall within a smallsize range. Furthermore, the expense of fine grinding is ratherconsiderable and adds materially to the cost of the final product.

ln general, it may be stated that the llotation of ore consisting ofrelatively large particles is attended with considerably more diilicultythan when the particles are of relatively smaller dimensions. In otherwords, it is generally more diflicult to iloat relatively large sizesylvite particles than it is to iloat relatively smaller particles. Ithas also been observed that the large sylvite particles make up asubstantial amount of the sylvite which is not floated and which is,therefore, usually lost in the tailings.

In a dotation operation, the ore is slurried in a liquid to prepare apulp of the ore. In a sylvite flotation process, the potash ore isslurried in a saturated brine solut1on to produce a brine slurry or pulpof from about 50% to about solids. The pulp is then reagentized with asuitable collector, diluted with brine, and passed to .a flotation cell.In the flotation cell the pulp is kept 1n circulation and is contactedwith air. Air bubbles adhere to the reagentized sylvite particles andfloat the sylvite particles. The sylvite float is raked ofi of the topof the flotation cell. Not all of the sylvite is floated oli' in thefirst flotation cell and the remaining pulp is removed as underflow fromthe first cell and is passed to a second ilotation cell. In the secondcell, the flotation operation is repeated, a sylvite concentrate isoated olf, and the remaining pulp may be passed to a third ilotationoperation. A flotation machine usually contains a plurality of suchcells associated together in series. After a series of flotationoperations, the remaining pulp, from which substantial amounts ofsylvite have been removed, is discarded as a tailing. This initialflotation operation is denominated a rougher flotation, the lloatproduct is denominated a rougher float or rougher concentrate, and thetailing is denominated a rougher tail.

The rougher concentrate, while containing substantially all of thesylvite values in the charged pulp, also contains a substantial amountof fine halite particles which were removed with the sylvite. Therefore,it is conventional practice to combine the rougher concentrate from theindividual otation cells and subject the combined rougher concentratesto a cleaner flotation operation. In the cleaner flotation operation,the rougher concentrate in a pulp is subjected to flotation in aplurality of flotation cells in series. The uniloated pulp recoveredfrom the last of the cleaner flotation cells is denominated a mid or amiddling and is usually recycled to the rougher cells. The float productfrom the cleaner operation is recovered as a high grade sylvite product,usually denominated a cleaner concentrate.

Since it is more difficult to float the larger sylvite particles ascompared with the smaller sylvite particles, in an operation as abovedescribed, considerable amounts of sylvite are lost as large sylviteparticles in the rougher tailings. This loss, of course, tends todecrease the eiliciency of the flotation operation and it is with theproblem of increasing the efficiency that the present invention isconcerned.

It is accordingly an object of the present invention to provide animproved process for the recovery of sylvite from potash ores.

It is another object of the present invention to provide an improvedflotation process for the recovery of sylvite from sylvinite ores.

It is a further object of the invention to provide an improved processfor the recovery of sylvite from sylvinite ores, which process includesa llotation operation and a sizing step.

These and other objects of the present invention will be apparent tothose skilled in the art as the description of the present inventionprogresses.

In accordance with the present invention, it has been discovered thateminently satisfactory beneiiciation of potash ores and minerals can beachieved by means of a series of critical and interdependent processsteps. Generally described, the present invention is a process forbeneiciating a potash ore which comprises slurrying a potash orecontaining sylvite with brine saturated at least with respect tosylvite, reagentizing the slurried ore with a reagent having apreferential affinity for the sylvite, subjecting the reagentized slurryto a first flotation operation in a plurality of rougher flotation cellsconnected in series, subjecting the flotation concentrate from at leastthe rst of the series of rougher ilotation cells to a second flotationoperation, separately recovering the fioat product of said secondflotation operation and the non-float product of said second dotationoperation, subjecting the flotation concentrate from at least the lastcells of the series of rougher dotation cells and at least a portion ofthe non-float product of said second iiotation operation to a sizingoperation, and separately recovering a line fraction and a coarsefraction from the hydroconing operation. The coarse fraction is asylvite material of high purity and may be recovered as a product or"the process.

In this novel process, potash ore containing sylvite, for example,sylvinite ore as received from the mine, is comminuted to economicalliberation size to produce a granular feed material. The comminution ofthe ore to the liberation ofthe various constituents is effected toliberate a substantial amount of the various constituents. it may bedesirable and economical to comminute the ore to liberate substantiallyall of the constituents; however, the ore may be liberated to a lesserextent, for example, to 7080% liberation. This granular material ispreferably sized to produce a granular feed of a particle size in therange of about -8 mesh. The comminution may be carried out dry or in asaturated brine and in any suitable comminuting apparatus such as a ballmill, rod mill, roller mill, hammer mill, or any other suitable type ofgrinding or crushing apparatus. When the ore is ground to the mesh sizeindicated, the sylvite values, halite values, and gangue values aresubstantially liberated from each other and the ore is ready for furthertreatment in accordance With this invention.

The ore While in a state of subdivision sufficient to substantiallycompletely liberate the desired components from the gangue is slurriedin a brine solution which is substantially saturated with respect tosylvite and also substantially saturated with respect to halite. Thesaturated brine is slurried with the comminuted ore to form a slurry offrom about 50% to about 75% solids, and reagents are introduced into theslurry and dispersed by agitation. The reagents used are cationic agentsand are added to selectively float the sylvite particles from the haliteparticles. Useful reagents are the collector agents selected from theclass of primary aliphatic amines of about C-ldr to C-2O length carbonchains and their acid addition salts, preferably the `acetate orhydrochlorides, for example, octadecyclamine acetate, hexadecylaminehydrochloride, and the like, of varying degrees of unsaturationdepending upon the temperature of the brine in which the flotationoperation is carried out. The amine reagents float potassium chloride.

After introducing the reagents having a preferential ainity for thesylvite constituents of the mixture, the slurry is diluted, preferablyto a solids concentration between about and about 35% solids, and thediluted slurry is passed to a rougher flotation cell. In the rougherflotation cell, in the presence of mechanical agitation and/or aeration,a froth is formed which carries the sylvite to the surface Where thefroth and its suspended solids are removed by overiiow from thevdotation cell. The removal of the iloated solids as overflow from thecell is usually promoted by the use of paddles or rakes which skim overthe surface of the brine in the cell and move the oat off.

The iiotation operation is carried out in a plurality of such ilotationcells associated together in series. Thus, in the first flotation cell,a large portion of the sylvite may be iloated out while still leaving inthe pulp a substantial amount of sylvite, and this is substantiallyremoved by a repetition of the floation process in the succeeding cellsto the end that the pulp passing from the nal cell containssubstantially none of the sylvite particles. Flotation machines having aplurality of ota-tion cells connected in series are commerciallyavailable and preferred machines are those referred to in the art asFagergren flotation machines and Denver flotation 4 machines. have fivecells connected in series.

As hereinbefore set forth, it has been noted that the larger sylviteparticles are more ditiicult to float as compared to smaller sylviteparticles. Therefore, some larger size sylvite particles tend to remainin the latter of the flotation cells in series. ln accordance with thepresent invention, the float products from this initial rougherflotation are separately collected in two float portions. Each floatportion includes the float from one flota-tion cell or from a pluralityof such cells in series. The first float portion which is separatelycollected includes at least the oat product from the iirst cell of theseries of cells and the second float portion which is separatelycollected includes at least the float product from the last cell of theseries of cells. Further, in accordance with the present invention, thelatter of the cells of the series, including the last cell, arepreferably operated so -that heavily overflowing conditions aremaintained so as to float oif larger sylvite particles.

The first float portion separately recovered from the rougher flotationoperation contains sylvite and some halite. To upgrade this first floatportion, it is passed to a cleaner flotation operation. The rst floatportion is of high solids content and, therefore, it is preferred toslurry it with saturated brine so as to obtain a slurry having a solidsconcentration of from about 20% to 35% solids. The rst float portionusually has suiicient cationic reagent present so that additionalcationic reagent is not necessary in the cleaner flotation; however, ifdesired, ybefore diluting the first float portion, it may be conditionedwith additional cationic reagent. The cleaner operation, like therougher flotation operation, is usually performed in a series offlotation cells. The cleaner oat is a product of high sylvite contentand is usually recovered as a nal product of the process. However, sincethe larger sylvite particles are more difficult to float, some of thelarger sylvite particles are not floated in the cleaner operation.Following the steps of the present invention, however, the lossesformerly encountered by the difficulty in floating these larger sylviteparticles are substantially reduced.

In accordance with the present invention at least a portion of thenon-oated portion from the cleaner flotation operation, usuallydenomina-ted mids or middlings, is combined with at least a portion ofthe second float portion collected from the rougher flotation operationand the combined stream is subjected to a sizing or Wet classicationtreatment. The combined stream contains substantial amounts of largersylvite and ne halite particles. The sizing or wet classification orhydroclassication substantially separates the larger sylvite particlesfrom the line halite particles. The sizing or hydroclassiiication may beperformed in any suitable manner such as by the use of rake classifiers,screens, etc.; however, the sizing is preferably performed in ahydroconing operation using at least one hydrocone. In a hydrocone aseparation is made in the cone-shaped part of the hydrocone by theaction of centrifugal and centripetal forces. The heavier material,which contains the major portion of the larger sylvite particles, leavesthe cone as underflow. The lighter material, which contains the majorportion of the tine halite particles, leaves the cone as overflow.

The underflow from the hydrocone is predominantly coarse sylvite.However, it usually still contains sorne tine halite. The ne halite maybe further removed by a further sizing operation which preferably is ascreening operation. The coarser fraction from the screening operationis substantially pure coarse sylvite. This coarse sylvite is preferablydewatered and dried and the dried material may be recovered as a productof the process.

In a preferred operation, at least a portion of the tine size fractionor cyclone overliow is recycled to the The Fagergren flotation machinesusually Y rougher flotation operation. It is also preferred that atleast a portion of the tine material which passed through the screen inthe screening operation be recycled to the rougher llatation operation.The recycling feature makes maximum use of the saturated brine andincreases recovery of sylvite.

Having generally described the process of the invention, a more specificand detailed description will be given with reference to theaccompanying drawing which is a diagrammatic flow sheet illustrating thegeneral application of the process of the invention.

Referring to the drawing, a reagentized sylvinite flotation feed or pulpis introduced through line 7 into a first ilotation cell 9 of a seriesof rougher flotation cells. The fresh feed in line 7 is combined with arecycle stream being recycled through line 11. The production of therecycle stream 11 will be hereinafter set forth. The fresh feed isprepared for ilotation by first comminuting and screening a potash oreto obtain a -8 mesh fraction, desliming the comminuted ore, andconditioning the deslimed ore in saturated brine at 60% solids contentfor two minutes with about 1.0 pound of potato starch and 0.15 pound ofaliphatic amine per ton of feed. The conditioned ore is then diluted to25 solids with saturated brine and the pulp is passed through line 7into the first flotation cell 9. A lloat fraction is Withdrawn from thellotation cell 9 through line 13 and the remaining non-floated pulp iswithdrawn through line 15 and passed to the second llotation cell 17. Inthe second llotation cell additional float product is withdrawn throughline 19. The noniloated pulp is withdrawn from cell 17 through line 21and is passed to the third flotation cell 23. In the third flotationcell additional float fraction is produced and is Withdrawn through line25. The noniloated pulp is withdrawn from cell 23 through line 27 and ispassed to a fourth flotation cell 29.

The lloat fractions in lines 13, 19 and 25 are combined in line 31 andthe combined iloat fractions are diluted fwith brine entering throughline 33 to produce a flotation feed containing 25% solids. The dilutedcombined float fractions are introduced through line 35 to a cleanerllotation operation in a series of cleaner llotation cells 37, 39, 41,43 and 45. The lloat products from each of these cleaner cells arerecovered and combined in line 47. The lloat product from the cleanercells is of high purity and may be recovered as a sylvite product of theprocess. The non-floated fraction removed from the last of the cleanercells 45, through line 49 contains substantial amounts of line halite aswell as substantial amounts of larger size sylvite and is furtherprocessed as is hereinafter set forth to recover the sylvite.

Referring back to the rougher llotation operation and specifically theflotation in the fourth rougher cell 29, the ilotation operation in thiscell 29 is conducted with a heavy overflow so as to facilitate therecovery of substantial amounts of the larger sylvite particles. Thelloat fraction is Withdrawn from cell 29 through line 51. Thenon-floated pulp is Withdrawn from cell 29 through line 53 and is passedto the fifth and last rougher flotation cell 55. This last rougher cellis also operated with a heavy overflow so as to float substantialamounts of the larger sylvite particles. The remaining non-floated pulpis Withdrawn from the last rougher cell 55 through line 57 and may bediscarded as a. waste tailing. The floated fraction is withdrawn fromthe last cell through line 59 and is combined with the float fractionfrom the fourth rougher cell 29 in line 61. The combined rougher floatfractions, 51 and 59, in line 61 are also combined with the non-lloatfraction 49 of the last cleaner flotation cell and the combinedfractions in line 63 are passed into a hydrocone 65 for a hydroconingoperation. The hydrocone 65 is a closed top cyclone. The feed materialin line 63 is fed tangentially into the hydrocone. The lighter portionof the feed introduced via line 63, which consists of line haliteparticles, leaves the cone65' as overllow through line 67 and isrecycled to the rougher llotation operation through lines 67 and 11l.

The heavier portion of the feed material introduced via line 63, whichconsists of larger or coarse sylvite particles, leaves the cone 65 asunderllow through line l69. The material in line 69 is screened inscreening zone 71 to further separate the sylvite from the fine haliteparticles. A screening on about 24 mesh has proven satisfactory. Thefine material passing through the screen 71 is withdrawn through line 73and is combined with the hydrocone overllow in line 67 and the combinedstreams in line 11 are reintroduced to the rougher flotation operationas above described.

The coarse material retained on the screen 71 is withdrawn through line75 and is dewatered and dried in zone 77. A coarse sylvite product iswithdrawn from dewatering and drying zone 77 through line 79.

In the foregoing description ve flotation cells were used in the rougherand cleaner operation; however, this was only for purposes ofillustration and it is to be understood that any suitable plurality canbe used in each of the llotation operations.

In a commercial embodiment of the present invention, an increase insylvite production of 2% was obtained by using this process as comparedto a conventional otation process using only a rougher and cleanerflotation operation.

The following example is given to illustrate a specic application of theinstant novel process and is not to be construed as limiting theinvention thereto.

Example A sylvinite feed material has the following size and mineralanalysis:

The sylvanite feed material was slurred with a saturated brine solutionto 60% solids. The slurried material Was then conditioned for twominutes with one pound of potato starch and 0.15 pound of aliphaticamine hydrochloride per ton of feed. The aliphatic amine used is sold byArmour & Company under the trade name Armeen and was neutralized withhydrochloric acid. The conditioned ore was then diluted to 25 solidswith saturated brine.

The diluted material was then subjected to a flotation operation at therate of 4200i g.p.m. in a standard flotation machine which has fivecells connected in series. The float sylvite products from the firstthree cells were separately recovered and combined. This combinedmaterial had the ilollowing size and mineral analysis:

The lloat products from the last two cells were separately recovered andcombined. This combined material had the following size and mineralanalysis:

Mesh Size Weight Percent Total Mineral Percent KZO Analysis 28.0 60.3Sylvite, 50%. 39. 59.0 Halite, 50%. 16. 0 45. 0 17.0 8.0

The combined float product from the first three rougher cells wasdiluted with saturated brine to 20% solids and was then subjected to astandard cleaner flotation operation at the rate of 1300 gpm. in a-Fagergren flotation machine which has three cells in series. TheSylvite float product recovered from the cleaner operation had thefollowing analysis:

Percent Sylvite 97 Halite 3 The middling recovered from the cleaningdotation operation had the following analysis:

Percent Sylvite 80 Halite 20 Mesh size-analysis: Percent l-l-IO 3 -}1414 14 i}20 62 2l Mineral analysis: Percent KCl 97 NACl 3 The overallrecovery of sylvite from the sylvinite feed was 88%.

The description of the invention utilized specific reference to certainprocess details; however, it is to be understood that such details areillustrative only and not by way of limitation. Other modifications andequivalents of the invention will be apparent to those skilled in theart from the foregoing description.

Having nofw fully described and illustrated the invention, what isdesired to be secured and claimed by Letters Patent is set forth in theappended claims.

We claim:

1. A process for the recovery of Sylvite from potash ores containingSylvite which comp-rises slurrying a potash ore containing sylvite ywithbrine saturated at least with respect to Sylvite, reagentizing theslurried ore with a reagent having a preferential affinity for theSylvite, subjecting the reagentized slurry to a first liotationoperation in a plurality of rougher cells connected in series,subjecting the flotation concentrate from at least the `first of theseries of rougher fiotation cells to a second :dotation operation,separately recovering the float product of said second flotationoperation and the non-float product of said second iiotation operation,subjecting the flotation concentrate from at least the last of theseries of rougher flotation cells while employing a greater overflowvolume of brine than employed in at least the first of said series ofrougher flotation cells and at least a portion of the non-float productof said second flotation operation to a sizing operation, and separatelyrecovering a small size fraction and a larger size fraction from thesizing operation.

2. A process for the recovery of Sylvite from a potash ore containingSylvite which comprises slurrying a potash ore containing sylvite, whilein a state of subdivision sufiicient to substantially completelyliberate the Sylvite from the other components of the ore with brinesaturated at least with respect to sylvite, reagentizing the slurriedore with a reagent having a preferential affinity for the sylvite,subjecting the reagentized slurry to a first flotation operation in aplurality of rougher flotation cells connected in series, recovering thefloat products from said first liotation operation in at least twoseparate portions, one lioat portion including the iioat product from atleast the first of the series of rougher flotation cells and the secondportion including the fioat product from at least the last of the seriesof rougher otation cells while employing a greater overflow volume ofbrine than employed in at least the first of said series of rougherflotation cells, subjecting said first portion to a second flotationoperation, separately recovering the fioat product of said secondfiotation operation and the non-float product of said second flotationoperation, subjecting the second float portion from said first flotationoperation and at least a portion of the non-float product of said secondflotation operation to a sizing operation, and separately recovering asmall size fraction and a larger size fraction from the sizingoperation.

3. A process for the recovery of sylvite from potash `ores containingSylvite which comprises slurrying a potash ore containing sylvite withbrine saturated at least with respect to sylvite, reagentizing theslurried ore with a reagent having a preferential afiinity for theSylvite, subjecting the reagentized slurry to a first flotationoperation in a plurality of rougher cells connected in series,subjecting the flotation concentrate from at least the first of theseries of rougher flotation cells to a second flotation operation,separately recovering the fioat product of said second fiotationoperation, subjecting the flotation concentrate from at least the lastof the series of rougher otation cells while employing a greateroverflow volume of brine than employed in at least the first of saidseries of rougher flotation cells and at least a portion of thenon-float product of said second iiotation operation to a hydroconingoperation, and separately recovering as overflow from said hydroconingoperation a fine fraction and as underfiow from said hydroconingoperation a coarse fraction of Sylvite which is removed from the processas a finished concentrate, and recycling at least a portion of said finefraction to said `first otation operation.

4. A process for the recovery of sylvite from sylvinite ore whichcomprises slurrying a potash ore containing sylvite, while in a state ofsubdivision sufiicient to substantially completely liberate the sylvitefrom the other components of the ore with brine saturated at least withrespect to Sylvite, reagentizing the slurried ore with a reagent havinga preferential aiiinity for the sylvite, subjecting the reagentizedslurry to a first fiotation operation in a plurality of rougherflotation cells connected in series, recovering the float products fromsaid first flotation operation in at least two separate portions, onefloat portion including the float product from at least the first of theseries of rougher flotation cells and the second portion including theoat product from at least the last of the series of rougher iiotationcells while employing a greater overfiow volume of brine than employedin at least the first of said series of rougher flotation cells,subjecting said first portion to a second flotation operation,separately recovering the float product of said second otation operationand the nou-float product of said second ilotation operation, subjectingthe second float portion from said first ilotation operation and atleast a portion of the nonoat product of said second flota-tionoperation to a classication operation, and separately rccovering a smallsize fraction and a larger size fraction from the classificationoperation, and recycling at leas-t a portion of said small size fractionto said first flotation operation.

5. A process for the recovery of sylvite from sylvinite ore whichcomprises slurrying a potash ore containing sylvite, while in a state ofsubdivision sufficient to substantially completely liberate the sylvitefrom the other components of the ore with brine saturated at least withrespect to sylvite, reagentizing the slurried ore with a reagent havinga preferential ainity for the sylvite, subjecting the reagentized slurryto a rst tlotation operation and a plurality of rougher otation cellsconnected in series, recovering the oat products from said rst dictationoperation in at least two separate portions, one iloat portion includingthe iioat product from at least the first of the series of rougherflotation cells and the second portion including the float product fromat least the last of the series of rougher otation cells While employinga greater overflow volume of brine than employed in at least the iirstof said series of rougher notation cells, subjecting said rst portion toa second ilotation operation, separately recovering the iloat product ofsaid second dotation operation and the non-oat product of said secondotation operation, subjecting the second float portion from said rstotation operation and at least a portion of the non-float product ofsaid second otation operation to a hydroconing operation, recycling atleast a portion of the overflow from said hydroconing operation to saidiirst notation operation, screening at least a portion of the underflowfrom said hydroconing operation and recycling at least a portion of thescreening underilow to said first dotation operation.

6. The process of claim wherein said screening operation is on about 24mesh.

7. A process for the recovery of sylvite from potash ores containingsylvite and halite which comprise slurry ing such an ore with brinesaturated at least with respect to sylvite, reagentizing said slurriedore with a reagent having preferential anity for the sylvite, subjectingsaid reagentizing slurry to a flotation operation :in a plurality ofrougher cells, connected in series, separately collecting an initialrougher flotation concentrate from at least the rst of the series ofrougher cells and a second rougher otation concentrate from at least thelast of the series of rougher otation cells while overflowing a greateramount of brine from these cells than is overilowed from at least therst of the series of rougher -flotation cells, and sizing the secondrougher otation concentrate into a sylvite fraction of large particlesize and a halite fraction of small particle size.

8. A process as in claim 7 wherein the second rougher otationconcentrate is screened to separate sylvite from halite.

9. A process as in claim 7 wherein the second rougher flotationconcentrate is subjected to a hydroconing operation to recover a sylvitefraction of large particle size and a halite fraction of small particlesize.

10. A process as in claim 7 wherein the initial rougher `flotationconcentrate is subjected to a cleaner otation operation in a pluralityof cleaner flotation cells connected in series, the underflow middlingsbeing sized into a small size fraction and a large size fraction, atleast a portion of said small size fraction being reintroduced into thesaid rougher ilotation operation and the overow cleaner sylviteconcentrate being processed to recover sylvite.

1l. A process as in claim 10 wherein the second rougher flotationconcentrate is screened to separate sylvite from halite.

12. A process as in claim 10 wherein the second rougher flotationconcentrate is subjected to a hydroconing operation to recover a sylvitefraction of large particle size and a halite fraction of small particlesize.

Fontein May 22, 1956 Bourne et al. Aug. 26, 1958

4. A PROCESS FOR THE RECOVERY OF SYLVITE FROM SYLVINITE ORE WHICHCOMPRISES SLURRYING A POTASH ORE CONTAINING SYLVITE, WHILE IN A STATE OFSUBDIVISION SUFFICIENT TO SUBSTANTIALLY COMPLETELY LIBERATE THE SYLVITEFROM THE OTHER COMPONENTS OF THE ORE WITH BRINE SATURATED AT LEAST WITHRESPECT TO SYLVITE, REAGENTIZING THE SLURRIED ORE WITH A REAGENT HAVINGA PREFERENTIAL AFFINITY FOR THE SYLVITE, SUBJECTING THE REAGENTIZEDSLURRY TO A FIRST FLOTATION OPERATION IN A PLURALITY OF ROUGHERFLOATATION CELLS CONNECTED IN SERIES, RECOVERING THE FLOAT PRODUCTS FROMSAID FIRST FLOTATION OPERATION IN AT LEAST TWO SEPARATE PORTIONS, ONEFLOAT PORTION INCLUDING THE FLOAT PRODUCT FROM AT LEAST THE FIRST OF THESERIES OF ROUGHER FLOTATION CELLS AND THE SECOND PORTION INCLUDING THEFLOAT PRODUCT FROM AT LEAST THE LAST OF THE SERIES OF ROUGHER FLOTATIONCELLS WHILE EMPLOYING A GREATER OVERFLOW VOLUME OF BRINE THAN EMPOLYEDIN AT LEAST THE FIRST OF SAID SERIES OF ROUGHER FLOTATION CELLS,SUBJECTING SAID FIRST PORTION TO A SECOND FLOTATION OPERATION,SEPARATELY RECOVERING THE FLOAT PRODUCT OF SAID SECOND FLOTATIONOPERATION AND THE NON-FLOAT PRODUCT OF SAID SECOND FLOTATION OPERATION,SUBJECTING THE SECOND FLOAT PORTION FROM SAID FIRST FLOTATION OPERATIONAND AT LEAST A PORTION OF THE NON-FLOAT PRODUCT OF SAID SECOND FLOTATIONOPERATION TO A CLASSIFICATION OPERATION, AND SEPARATELY RECOVERING ASMALL SIZE FRACTION AND A LARGER SIZE FRACTION FROM THE CLASSIFICATIONOPERATION, AND RECYCLING AT LEAST A PORTION OF SAID SMALL SIZE FRACTIONTO SAID FIRST FLOTATION OPERATION.